Coaxial rotary joint



p 1961 w. J. MOULDS 2,999,218

COAXIAL ROTARY JOINT Filed Dec. 29, 1959 2,999,218 CDAXIAL RQTARY JOINTWilliam J. Moulds, Albuquerque, N. Mere, assignor to the United Statesof America as represented by the Secretary of the Air Force Filed Dec.29, 1959, Ser. No. 362,731 1 Claim. (Cl. 339-8) (Granted under Title 35,US. Code (1952), sec. 266) The invention described herein may bemanufactured and used by or for the United States Government forgovernmental purposes without payment to me of any royalty thereon.

This invention relates to a coaxial rotary joint for obtaining data froma rotating system for application to a stationary system or device suchas an oscilloscope.

One object of the invention is to provide a rotary joint with lowattenuation and low noise generation within the range of from 0 to 250rpm.

This and other objects will be more clearly understood from thefollowing detailed description taken with the drawing, wherein:

FIG. 1 shows a front elevational view partially in section of a rotaryjoint according to the invention.

PEG. 2 shows a full sectional view of the device of FIG. 1 along theline 2-2.

FIG. 3 shows a full sectional view of the device of HG. 1 along the line33.

Referring more particularly to FIG. 1 of the drawing which shows arotary joint having a movable assembly 11 and a stationary assembly 12.

The stationary assembly consists of an upper cylindrical housing 13,with a polished inner surface, a lower housing 14, an upper plate member15, a lower plate member 16, an upper bearing 17 and a lower bearing 18.

The upper housing 13 has four studs 20, two of which are shown in thisfigure extending out of the upper end thereof and four studs 21, threeof which are shown, extending out of the lower end. The upper bear-ing17 and upper plate member 15 are secured by means of nuts 22 and thelower bearing 18, the lower housing 14 and the lower plate member 16 aresecured by means of nuts 23. in the device built the upper and lowerhousings, the upper and lower plate members and studs were made of brassand the upper and lower bearings were made of Teflon, but it is obviousthat other materials could be used if desired.

The rotating assembly consists of a connector member, having an innerconductor 26 and an outer conductor 27 which are separated by means ofan insulator 28.

The connector member rotates together with the apparatus to which it isattached at 19 within bearings 17 and 1-8 and is held in place by meansof flange 29 and shoulder 30. The outer conductor of the rotor assemblyis connected to the outer conductor of a cable 31 by means of a pair ofwipers 32 made of beryllium copper springs 33 with silvered contactbuttons 34. The buttons 34 wipe against the polished inner surface ofthe upper housing member 13 which is connected to the outer conductor ofcable 31 through brass stud bolts 21, the lower plate member 16 andflange 24. The wipers are attached to the outer conductor 27 by means ofscrews 35.

The inner conductor 26 is connected to the inner conductor of cable 31by means of a pair of wipers 40 made of the same material as wipers 32which wipe against the polished surface of a copper disk 42. The disk 42is connected to the inner conductor 26 at 43. A Teflon ring 44 fits overouter conductor 27 and has a brass ring 45 fitted around the end thereofadjacent disk 42. Disk 42 is silver soldered to ring 45 to add supportfor disk 42. The space between outer conductor 27 and disk 42 should begreat enough to prevent a short. For device shown the spacing is .031inch. A static brush mount 46 is secured to the lower plate member 16 asshown in FIG. 3.

The springs 47 for wipers 40 are attached to brush mount 4d by means ofscrew 43 as shown in FIG. 3; The inner conductor of cable 31 isconnected to springs 47 at this point.

The device has been tested for a frequency range from DC. to 20 MC.while rotating up to 400 rpm. with less than 0.5 millivolt of noisegeneration. The device has also been tested with 0.1 microsecond pulsesand found to be satisfactory.

There is thus provided a coaxial rotary joint with low attenuation andlow noise generation.

While certain specific embodiments have been described in some detail,it is obvious that numerous changes can be made without departing fromthe general principles and scope of the invention.

I claim:

A joint for connecting a rotating coaxial system to a stationary coaxialsystem comprising; a cylindrical electrically conductive housing havinga portion of the inner surface polished, a first electrically conductiveplate member attached to one end of the housing, a second plate memberattached to the other end of the housing, means for connecting thehousing to the outer conductor of the stationary coaxial system throughthe first plate, a first bearing member located within the housing andspaced between the first and second plates, a second bearing memberlocated within the housing and adjacent to the second plate, a coaxialconnector member rotatable and supported within said bearings, thecoaxial connector member having an inner conductor member and an outerconductor member insulated from one another, the outer conductor memberadapted to be connected to the outer conductor of the rotating coaxialsystem and the inner conductor member adapted to be connected to theinner conductor of the rotating coaxial system; a plurality of springWiper elements connected to and rotatable with the outer conductor ofthe coaxial connector member, each of the wiper members having a contactbutton, the contact buttons engaging the polished inner surface of thehousing during rotation of the connector member; an electricallyconductive disk connected to and rotatable with the inner conductor ofthe connector member and spaced from the outer conductor, one surface ofthe disk being polished, an insulating wiper mount mounted in thehousing adjacent the first plate, a plurality of stationary springwipers having contact buttons mounted in the hous ing on the wipermount, the contact buttons of the stationary wipers engaging thepolished surface of the disk during rotation of the disk and means forconnecting the stationary wiper elements with the inner conductor of thestationary coaxial system.

References Cited in the file of this patent UNITED STATES PATENTS1,657,306 Gursky Ian. '24, 1928 1,925,095 Halliburton Sept. 5, 19332,190,295 Miller et a1 Feb. 13, 1940 2,473,526 Hood et a1. June 21, 1949FOREIGN PATENTS 89,032 Switzerland Apr. 16, 1921

